Loading ramps to provide a bridge between a loading dock and the bed of a vehicle to be loaded or unloaded is a well developed art. In its basic form the prior art apparatus includes a platform or ramp which is automatically raised by release of a spring, the actuation of a hydraulic motor, the release or falling of a weight or perhaps a motor designed to raise the ramp by gear connections.
Ordinarily, the pivotable ramp is mounted on a frame built into a pit in the loading dock. Traditionally, the upper surface of the ramp will be coplaner with the surface of the loading deck. The rear edge of the ramp is pivoted about an axis at or near the level of the loading dock and the forward end of the deck includes a lip which is pivotable and projectable to lie on the bed of the vehicle to be serviced.
By whatever means, the ramp will be raised and then the workman will walk out on the raised ramp. Some automatic or semi-automatic mechanical structure comes into play to project the lip progressively as the ramp itself is "walked down" on some newer models, but for the most part, the lip will be projected by some mechanical apparatus on the upswing. At some stage during the walk down process the lip projecting means is slowly released by the projecting means and a lip lock holds the lip in projected position. The lock is usually released by gravity or springs when the lip engages the truck bed.